Books where a couple people get together to solve crimes/mysteries that already took place

I am looking for books like Tokyo Zodiac Murders where the crime happened long ago and the clues are already available and a couple people get together to talk about the crime and solve it.

A while ago in some thread someone recommended a book where two legal interns or something are assigned a case and they solve the whole thing while going through the files. I couldn't find it but something like that is also fine.